Perhaps snail trail is back, inspiring a tantrum (9)
I believe the answer is:
gastropod
'perhaps snail' is the definition.
(snails are gastropods)
'trail is back inspiring a tantrum' is the wordplay.
'trail' becomes 'dog' (synonyms).
'is back' is a reversal indicator (I've seen 'be back' mean this).
'inspiring' is an insertion indicator.
'tantrum' becomes 'strop'.
'dog' in reverse letter order is 'god'.
'a'+'strop'='astrop'
'god' going around 'astrop' is 'GASTROPOD'.
(Other definitions for gastropod that I've seen before include "sluggish type" , "Could be snail" , "Little creature" , "Slimy type" , "slug, perhaps" .)